the $14Bn they are making selling electronics.
Yet Another Anonymous coward,
You mistake turnover for profits. Something I am beiginning so suspect that Jeff Bezos may be doing too. They don't make $14bn on sales of electronics. They buy about $14bn of electronics from other people, and sell them for hopefully a higher number. That difference is their gross profit. From which you take their costs to work out how much cash they have left to blow on winning market share in other markets.
They may have mostly killed the large book and music chains, but that doesn't mean they can massively up their prices. There are plenty of other online companies around, and as Amazon proved, it's much easier and cheaper to set up online, so they'll never be safe from competition.
So I'm sure they can outspend Rackspace, but not Google or Microsoft. Remember Google and MS have to have huge datacentres already, to do the other that makes them profits. So they are only adding to infrastructure they've already built and must maintain to survive.
Amazon make losses (or sometimes break even) every quarter, and say it's because they keep re-investing it into new bits of the company. MS and Google also invest lots of money in bits of the company and yet they make profits each quarter. MS about $5bn, Google about half that.
Which means that either of them could invest as much money as Amazon does on cloud infrastructure again, and still be making healthy profits, despite the fact they already invest as much or more than Amazon do.
One certainty is that Amazon cannot outspend them. And that's to ignore IBM, Oracle, HP and I suppose even Apple. Any of those could afford to blow a few billion a quarter on datacentres if they want to.